After Clicked Several Times The Sword Works, Why Do I Get This Error?

Though the sword works, eventually after I click three times I get this error once and never again, because the sword works after that. Why do I keep getting this error even though the sword works?

.SwordScript:48: attempt to index global 'hitHumanoids' (a nil value)

Here is the script:

-- Made by Prime Alphinex

tool = script.Parent

local event = tool:WaitForChild("RemoteEvent")
local handle = tool:WaitForChild("Handle")
local debris = game:GetService("Debris")

local slashSound = handle:WaitForChild("SlashSound")
local overheadSound = handle:WaitForChild("OverheadSound")
local lungeSound = handle:WaitForChild("LungeSound")

local speedBoost = 1.25
local damage = 19
local swingTime = 1
local comboWindow = 0.5
local lastClick = tick()
local combo = 1

tool.Activated:connect(function()
    local clickDelta = tick() - lastClick
    if clickDelta > swingTime then
        hitHumanoids = {}
        lastClick = tick()
        if clickDelta < swingTime + comboWindow then
            combo = (combo + 1) % 4
        else
            combo = 1
        end
        if player then
            if combo == 1 then
                event:FireClient(player, "RunAnim", "SlashAnim2")
                slashSound:Play()
            elseif combo == 2 then
                event:FireClient(player, "RunAnim", "ThrustAnim2")
                overheadSound:Play()
            elseif combo == 3 then
                event:FireClient(player, "RunAnim", "OverheadAnim2")
                lungeSound:Play()
            end
        end
    end
end)

handle.Touched:connect(function(hit)
    if equipped and character and humanoid and humanoid.Health > 0 and hit and not hit:isDescendantOf(character) then
        local targetHumanoid = hit.Parent:FindFirstChild("Humanoid")
        if targetHumanoid and targetHumanoid.health > 0 and not hitHumanoids[targetHumanoid] then
            hitHumanoids[targetHumanoid] = true

            for _, v in pairs(targetHumanoid:GetChildren()) do
                if v and v.Name == "creator" then
                    v:Destroy()
                end
            end
            local tag = Instance.new("ObjectValue")
            tag.Name = "creator"
            tag.Value = player
            debris:AddItem(tag, 3)
            tag.Parent = targetHumanoid

            targetHumanoid:TakeDamage(damage*combo)
        end
    end

end)

tool.Equipped:connect(function()
    equipped = true
    lastClick = tick()
    combo = 1
    character = tool.Parent
    player = game.Players:GetPlayerFromCharacter(character)
    humanoid = character:FindFirstChild("Humanoid")
    if humanoid then
        humanoid.WalkSpeed = humanoid.WalkSpeed * speedBoost
    else
        character = nil
    end
end)

tool.Unequipped:connect(function()
    local equipped = false
    if humanoid then
        humanoid.WalkSpeed = humanoid.WalkSpeed / speedBoost
    end
    character = nil
    humanoid = nil
end)